The present invention relates to an arrangement for managing/monitoring routing in a communications network, comprising a routing domain within a number of routing areas containing network nodes communicating via transmission links, which implements link state routing. The invention also relates to a routing controlling device for controlling routing in a routing area in a network implementing link state routing at least for that part (area) of the network. The invention also relates to a method of controlling routing within a routing area implementing link state routing. By controlling is here meant managing and/or monitoring.
Through routing a path through a network is determined. This can be done in different manners. Generally the monitoring and the management of the routing process is performed through direct communication with all network nodes which are associated with the routing process. According to one known solution this is done through actual login on each network element and retrieval of information. This is disadvantageous since each network node has to be contacted which means that network resources will be required which means that bandwidth as well as CPU (Central Processing Unit) power is demanded within the network nodes which is disadvantageous since preferably bandwidth as well as CPU power are scarce resources which should be used, to an extent which is as high as possible, for actual traffic handling. Another disadvantage consists in that the actual login on each network node generally is slow and different procedures are needed for different kinds of network nodes, for example different procedures are required for different manufactures of network nodes.
Alternatively remote monitoring may be implemented. Then may for example the SNMP (Simple Network Management Protocol) be used.
This is for example described in RFC 1157. This is however slow due to the fact that network nodes treat SNMP messages with the low priority as compared to other messages relating to other functions. A particular issue relates to Internet routing. Routing is a process used by Internet hosts for delivery of packets. Internet uses a hop-by-hop routing model which means that each host or router handling a packet examines the destination address in an IP header, computes the next hop address which will bring the packet one step closer to its destination and delivers the packet to the next hop address. There the above mentioned process is performed over again. A routing table is then required for matching destination addresses with next hops and routing protocols determine the contents of the tables. One particular kind of a routing protocol is a link-state routing protocol. Such a protocol requires each router to maintain at least a partial map of the network. When a link in the network changes its state (up to down or vice versa), a notification called a Link State Advertisement (LSA) is flooded throughout the network. This means that all the network nodes, in the case of Internet routers, note the change and in agreement therewith compute the routes. Examples on Internet links state routing protocols are OSPF (Open Shortest Path First) and ISxe2x80x94IS (OSI, Open Systems Interconnection). OSPF version 2 is for example described in RFC 1583. OSPF uses small so called hello packets for verification of link operations without transferring large tables. According to OSPF the routing domain is divided into different routing areas comprising a backbone area which divides interior routing into two levels and if inter area traffic is required, the packets are first routed to the backbone which is such may cause non-optimal routes since the inter area routing is not carried out until the packet reaches the backbone.
Link state routing of Internet means that each router has to find out which its neighbours are and obtain information about their addresses, measure the delay or the cost to each of said neighbours, construction of a packet with the above mentioned information which packet is to be sent to all the other routers and computation of the shortest path to all the other routers.
In addition to the hop-by-hop model another model is known which is denoted xe2x80x9csource based routingxe2x80x9d. The difference is that, the route that a packet should take through a network is determined at the network ingress point and not like in the hop-by-hop model where it is determined at every node that the packet traverses. This model is used e.g. in ATM and PNNI.
U.S. Pat. No. 5,687,168 for example describes link-state routing in an ATM communication system. A link-state routing device is here used to reduce the amount of link state information that is exchanged in the network irrespectively of the number of links connecting adjacent switches. An abstracted link a plurality of links are virtually aggregated to generate a link state with respect to the abstracted link uniting link state information of a plurality of links. The link state update protocol portion has link topology the information synchronized on the network through distribution of the abstracted link-state information with the flooding mechanism. Because of the fact that the abstracted link represents a plurality of links, the amount of information to be distributed can be reduced. However, this document discloses no solution to the above mentioned problems.
What is needed it is therefore an arrangement as referred to above for managing/monitoring routing in a communications network comprising a number of routing domains in turn comprising a number of routing areas with a number of network nodes which communicate via transmission links. Each routing domain is administrated as one unit by administrating means and link state routing is implemented through which the management, which may comprise monitoring and/or managing of new situations on transmission links within the network, in an efficient, reliable and cheap manner, can be provided. An arrangement is also needed through which routing monitoring/management can be handled in such a manner that bandwidth can be saved both generally in the network and for the respective network nodes and through which CPU power can be saved for the respective network nodes. An arrangement is also needed through which routing managing and monitoring can be handled in a fast manner as well as independently of kind of network node, manufacturer of network node etc.
Therefore is also a routing controlling device for managing/monitoring routing within a routing area needed through which the above mentioned objects can be fulfilled.
Still further a method of managing/monitoring routing within a routing domain or in a routing area as referred to above is needed through which the above mentioned objects can be met.
Therefore an arrangement as referred to above is disclosed and there is one link state database for each routing area within the routing domain. A domain may of course comprise only one routing are as well. A link database is maintained by each network node of the routing area that each network node belongs to since each network node belongs to at least one routing area. For at least some of the routing areas a separate routing controlling device is provided such that a domain with a plurality of routing areas may comprise also a plurality of routing devices; and there may be one routing controlling device for each area but it is not necessarily the case. The numbers may also differ. Such routing controlling device belongs to the routing process of the respective routing area and it contains a copy of, preferably an identical copy of, the link state database of the routing area or areas and it is/are identical to the link state database of the network nodes of the respective area. Each routing controlling device is connected to a network node of the respective routing area it belongs to and the routing controlling device comprises means for rejecting non-routing information/traffic and for injecting routing information into the link state routing process respective routing area. More generally means are provided for preventing non-routing information from reaching the routing controlling devices, which only accept routing information (not traffic). Particularly there is one routing controlling device for each routing area. In an alternative embodiment at least one routing controlling device belongs to more than one routing area. As referred to above, a routing domain may comprise more than one routing area. In a preferred implementation the means for injecting routing information comprises means for injecting a link state database records of the respective links state routing process into the link state process of the respective area or areas it belongs to. In a particular implementation a routing controlling device is only connected to one network node of the area it belongs to. However, it may also be connected to more than one network node of such area. It may also be connected to a network node belonging to more than one routing area or it may be connected to a routing device of each of more than one area.
In a preferred implementation the routing controlling device(s) monitor and/or manages updates/changes in the network nodes of the respecting routing areas. Particularly the routing controlling devices operate in such a manner that they simulate the network nodes of its routing area(s) through injecting messages to routing process(es) of the respective routing area(s) when there for example has been a change on a link connected to network node so that a message appears to be issued by said network node for purposes of fulfilling the used protocol, for example a standard protocol which require that the messages actually are issued by the network nodes themselves.
In a particular implementation the network is Internet. Then at least some of the network node comprise Internet routers. According to one embodiment the used link state routing protocol is then OSPF (Open Shortest Path First). The administrating means handling the routing domain as one single unit may be an Internet Service Provider (ISP).
Particularly the routing protocol comprises a link state update protocol and a link state acknowledgment protocol to ensure that all network nodes, particularly routers, within the routing area actually comprise the same link state database. The network nodes, or particularly the routers, particularly send so called link state acknowledgments, in short LSAs between each other and for each destination of a packet or a message, the network node or the router uses an algorithm to find the shortest path. Although here is mainly referred to a router, it may also be a switch or some other network node. The routing controlling device operates in such a manner that it transforms a network change, i.e. a change on a link to/from a network node, within its area (or within one of its areas) in case it is connected to more than one routing area, into LSA records particularly through manipulating LSA records in the link state database. The manipulated LSA records are then flooded throughout the respective routing area that is concerned (or which areas are concerned).
In a particular implementation the network is an ATM (Asynchronous Transfer Mode) network. In such a communication system the network nodes comprise switches and for example the PNNI (Private Network to Network Interface) link state protocol may be used.
Therefore also a device for controlling routing within a routing area of a routing domain provided. The routing area, as referred to above, comprises a number of network nodes which communicate via transmission links and link state routing is implemented in the area. The network nodes may comprise Internet routers or switches of an ATM communication system. Each network node comprises a link state database which is the same for all nodes within the same routing area, i.e. it is assured that it is the same and the same information is comprised in every network node. The routing controlling device comprises a copy of the link state database of the routing area, i.e. it is identical to the link state databases of the network nodes. The routing controlling device may be provided for one or more than one area. Means for rejecting non-routing information to the routing controlling means are provided. Moreover means are provided for injecting routing information into the link state routing process of the area. This means that the device only handles routing information (and thus not the traffic to be routed like other network nodes do) and it is connected to at least one network node. The routing controlling device may also be connected to a network node which via transmission links is connected to network nodes in for example two areas. Such routing controlling device may also be connected to for example two network nodes within one and the same routing area.
Particularly the means for injecting routing information injects transformed link state database records into the link state routing process. Particularly the network controlling device simulates the network nodes of its routing area(s) through injecting messages or database records when there for example has been a change on a transmission link such that the message actually appears to be issued by the concerned network node that is connected to the transmission link since known protocols require that the network nodes actually emit the messages. This can be provided for in different manners. Particularly the device is used for monitoring and/or handling or managing updates/changes concerning the network nodes of the its area(s).
Therefore also a method of controlling routing in a routing area of a routing domain, wherein the routing area comprises a number of network nodes, is provided which implements link state routing. The method comprises the steps of; providing a routing controlling device for the routing area which only handles information messages relating to routing; providing a copy of the link state database as provided in each network node of the routing area also in the routing controlling device so that the device forms part of the routing process of the routing area; providing information to the routing controlling means relating to updates/changes within the routing area; transforming the updated/new information into link state acknowledgments (link state database records) in the routing controlling device; sending the link state database records (new LSA:s) to the network nodes within the routing area from the routing controlling device/flooding the updated information into the routing area and updating the link state databases.
Particularly the method comprises the steps of; controlling more than one routing area from one routing controlling device; maintaining a copy of the link state database of each routing area controlled by the routing controlling device in the routing controlling device; providing the network nodes of the respective area with the updated information of the respective area through sending LSA:s of the respective routing area to the network nodes of the appropriate area.
Routing monitoring/management according to the present invention may particularly be used for routing different types of traffic as disclosed in the copending patent application xe2x80x9cAn arrangement, a system and a method for routing traffic in a networkxe2x80x9d filed by the same applicant and at the same day as the present application, which herewith is incorporated herein by reference. The invention disclosed herein is based on separation of IP traffic in a routing domain.
It is an advantage of the invention that not each network node has to be contacted or communicated with for management/monitoring when a change or an update takes place etc. which has as a consequence that bandwidth as well as CPU power can be saved for the network nodes. It is also an advantage of the invention that routing management gets fast and efficient and that the same procedure can be used irrespectively of kind of network node, particularly irrespectively of network manufacturer.